Acid arsenate of lead.



J portance when using it CLARE H. HALL, OF MILWAUKEE, WISC ONSIN, ASSIGNOR TO CORONA CHEMICAL COMPANY, OF MILWAUKEE, WISCONSIN, A CORYORATION OF WISCONSIN.

ACID ARSENATE OF LEAD.

Ho Drawing.

To all whom it may concern Be it known that I, CLARE H. HALL, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented a new and useful Improvement in Acid Arsenat-e of Lead, of which the following is a specification.

My invention consists in a novel material which is chemically acid arsenate of lead (PbHAsOQ having certain novel and valuable physical properties particularly suiting it for use as an insecticide.

Acid arsenate of lead, when used as an insecticide, is mixed with a relatively large quantity of water, usually 1 part of the acid arsenate to 400 parts of Water by weight, and the physical mixture thus formed is sprayed 'upon the plants to be treated. Sincethe acid arsenate of lead is practically insoluble, the resultant mass is simply a physical mixture, and it is of the utmost im? that the acid arselead be of such physical consistency as to remain suspended in the liquid, without substantial settling, during the period which will be occupied by the spraying.

The acid arsenate of lead has heretofore been-made by precipitating from one or an other of the various combinations of salts which will produce it, and the resultant mass has been treated in a filter press to form a pulp. In most cases, this pulp is the commercial product, the pressure being such as to leaveabout 50 per cent. of water by weight in the mass. In some cases, this pulp has been dried ahd pulverized, the dry a-cid' arsenate of lead being sold in the form added to and stirred in the requisite amount of powder. In use, both products have been of water.

It has been found that the drying and pulverizing of the pulp, in practically every case, greatly increases its settling tendency, and, for that reason, prior to my invention,

nate of the pulp has been in greatest demand. The p p, vantages. packing. and shipping,

shipping In the second place,

however, has certain important disad- In the first place, the expense of as compared with the dry product, is

packing and the pulp considerable.

Specification of Letters Patent.

Application filed March 1,

Patented June 10, 1913.

1913. Serial No.751,465.

in the hands of the consumer or middleman frequently dries out into a cake which can not be mixed with water and which is therefore useless. In the third place, there are very stringent Federal requirements as to the percentage of water permitted in the pulp, and from the manufacturingpoint of view it is an exceedingly difiicult matter to maintain the percentage constant, so that one part of a given batch may have per cent. water, while another has 45 per cent, with the result that the manufacturer may unwittingly subject himself to criminal prosecution. In spite of these disadvantages, however, the superior suspension properties of the pulp have led to its being the most popular form of acid arsenate of, lead. I have succeeded, however, in producing a dry arsenate of lead of the composition PbHAsO, which remains in suspension in water as well as any of the pulps heretofore manufactured and far better than any of the dry material of similar chemical composition. The difference in this property is of course caused by a difference in physical constitution, andthe material is obtained by employing several steps which coiiperate to this end. 7

As a first step, it is desirable that the material be thrown down in the form of the most minute possible particles, and this re sult can be produced by using extremely dilute solutions of the reacting salts; as, for instance, sodium acid arsenate, Na. .HAsO,, and lead nitrate, Pb(No,),, the nitrate of lead being formed in a solution of 1 part of nit-rate of lead to 150 parts of water, and the sodium acid arsenate being introduced ina relatively strong solution, say 1 part to 10 parts of water and at slow speed. The precipitate thus formed is so fine and flocculent as to make it a matter of some difficulty to press it to the dryness at which commercial pulps are regularly sold. This-fine precipitate is pressed in the filter press to what is known as a 3537 per cent. pulp, that is, a pulp in which the solid matter is by weight approximately 35 per cent. and the water approximately 65 per cent. of the cake. The cake is ejected from the filter press, dried, and pulverized in a pul- As the temperature of the waterhas a dethe following manner:,In this test 15 verizer of the disintegrator type, after it has been broken up into pieces of a convenient size-say pieces which will pass an inch mesh. The resultant material is a fine, exceedingly'light powder. While the dry bulk of the material, uncompressed, has little relation with the important quality of the length of time itwill remain suspended in Water, it may be stated as a fact,'for purposes of identification, that the present product has, in fact, a rather high dry bulk, about 100 cubic inches or more to the pound, and this is a considerably larger dry bulk than that of the other dried products now available. It will be understood, of course, that this dry material can be compressed somewhat in packing, and the foregoing figure has reference merely to its unpressed condition as it emergesfrom the pulverizer in marketable condition.

he most distinctive and important quality o the present material lies in its capacity for remaining suspended in Water, in which it far excels all other dry materials now available. Since there is no recognized standard for determining or measuring this quality, I have devised a test to which I have submitted the various forms of acid arsenate of lead available, which test is performed in grams of the arsenate of lead is pulped with water and diluted until the total volume is 250 c. c., the mixture being performed in a cylindrical glass graduate of this capacity and withadiameter of approximately 1% inches.

cided' influence on the settlement, a temperature of very close to'15 O. has been used. The density of warm water being much less than cold, the settlement is noticeably faster at temperatures above 15 C. and noticeably slower at temperatures below 15 C. The acid arsenate of lead of course begins to settle, and after a short time a distinct space. of clear water canbe seen above, the lower part of the graduate remaining full of the white opaque mixture. In making the test which I have devised, the location of the line of separation between the clear water and the mixture is observed at intervals, and I-have learned that of 5 minutes, the line of'separation is at 210 'c. 0. mark, at the end of 10 minutes, at 17 5 similar tests on the pulps in their commercial condition. The foregoing rate of set my product settles in the following manner: At the end tlement'is as slow as that of any of't-he pulps, and it far exceeds that of any of the dry materials available. For practical purposes, manifestly the rate of settlement during the first 10 minutes is the important point, and although the rates of settlement of the different materials in the main correspond, I have discovered some instances where materials settle relatively slowly during the first 10 minutes and relatively fast thereafter. However, my material not only settles slower, but settles much slower during the first 10 minutes than any products available. In fact, the slowest settlement which I discovered with a dry product was 165 at the end of 5 minutes, and 105 at the end of 10, minutes, and the largest final settlement which I observed was 45 at the end of 24a hours, as against 68 for my product.

It is thus evident that my product, while chemically the same as other materials sold for the urpose, has radical differences in its physical form, which, differences are readily distinguishable by the simple settling test above outlined. It is also a fact that this physical test is directed immediately at the single quality of greatest utility in practice.

It will be understood by those skilled in the art that there are two well-known forms of lead ars'enatethe acid arsenate which I have described, and the neutral arsenate, Pb (AS041) and there is, intermediate substance which may be a true chemical compound or may be a mixture. These various products are marketed in accordance with the percentage of arsenic which they contain, these percentages being, roughly, 33, 28 and'25 for the acid, the intermediate and the neutral arsenate. As a general proposition, the intermediate and the neutral arsenates settle more rapidly-because of their higher specific gravity.

- The present invention has reference only to the acid arsenate as described, but it is to be understood that I intend to cover the same commercial material whether it have materials low in arsenic or not.

I claim as new and desire to secure by Letters Patentr 1 1'. The herein-described dry, soft, white der essentially acid arsenat'e of lead (PbHAsOJ distinguished by the fact mixed wit-h water in the percentage of 15 grams to a total volume of 250 c. c., and allowed to settle the line of demarcation between the clear and clouded parts of the fluid is'not below 175 c. c., at the end of 5 minutes, and not below 140 c. c., at the end of 10 minutes.

2. The herein-described dry, soft, white bulky powder essentially acid arsenate of lead (PbHAsO,) distinguished in addition, an

by the fact of the dry I ioo .mixed with it a certain percentage of the that when mixed with water in the per- In testimony whereof I hereunto set my centage of 15 grams to a total volume of 250 hand this 24th day of February, 1913. c. 0., the line of demarcation between the i clear and clouded parts of the fluid is ap- CLARE HALL 5 proximately at 210 c. c. at the end of 5 min- In presence of two subscribing witnesses:

utes and approximately at 17 5 c. c. at the D. O. THORSEN,

end of 10 minutes. a O. G. AvIsUs.

It is hereby certified that in Letters Patent No. 1,064,639, granted June 10, 1913, upon the application of Clare H: Hall, of Milwaukee, Wisconsin, for an improvement in Acid Arsenate of Lead, an error appears in the printed specification requiring correction as follows: Page -1 transpose lines 59 and-t0; and thatthe said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 23rd day of December, 1)., 1913.

[SEALr] I J T. NEWTON,

Acting Commissioner of Patents;

that when mixed with water in the per- In testimony whereof I hereunto set my centage of 15 grams to a total volume of 250 hand this 24th day of February, 1913. c. 0., the line of demarcation between the i clear and clouded parts of the fluid is ap- CLARE HALL 5 proximately at 210 c. c. at the end of 5 min- In presence of two subscribing witnesses:

utes and approximately at 17 5 c. c. at the D. O. THORSEN,

end of 10 minutes. a O. G. AvIsUs.

It is hereby certified that in Letters Patent No. 1,064,639, granted June 10, 1913, upon the application of Clare H: Hall, of Milwaukee, Wisconsin, for an improvement in Acid Arsenate of Lead, an error appears in the printed specification requiring correction as follows: Page -1 transpose lines 59 and-t0; and thatthe said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 23rd day of December, 1)., 1913.

[SEALr] I J T. NEWTON,

Acting Commissioner of Patents; 

